1. Technical Field
This invention relates to line printers in general, and more particularly, to hammer banks for line printers that are both easier and lower in cost to manufacture and service.
2. Related Art
Line impact matrix printers, or line printers, produce letters and graphics in the form of a matrix of dots by employing a “shuttle” mechanism that runs back and forth in a horizontal direction over a page of a print medium, such as single sheet or continuous form paper, coupled with movement of the page perpendicular to that of the shuttle. An inked “ribbon” is typically interposed between the shuttle and the page. The shuttle comprises a “hammer bank,” i.e., an inline row of cantilevered, magnetically retracted hammer printing tips respectively disposed on the ends of elongated spring fingers, or “hammers,” each of which is selectively “triggered,” i.e., electromagnetically released, and timed so as to impact the page through the ink ribbon and thereby place a dot of ink on the page. As a result of the ability to precisely overlap the ink dots produced thereby, line printers can produce vertical, horizontal and diagonal lines that have a solid appearance, and print that closely resembles that of “solid font” printers, and refined graphics similar to those produced by graphics plotters, at speeds of up to 2000 lines per minute. Additionally, because the printing involves impact or mechanical pressure, these printers can also produce carbon and carbonless copies.
Examples of hammer banks for line printers can be found in the patent literature, including U.S. Pat. Nos. 6,779,935 and 6,821,035, both to John W. Gemmell, the respective disclosures of which are incorporated herein by reference. While these and other prior art line printer hammer banks can provide satisfactory print quality and speeds, they are not without some drawbacks.
For example, prior art hammer banks typically comprise a machined or die cast base part that is relatively expensive to make, and which is substantially integrated in the shuttle mechanism, which makes both the shuttle mechanism and the hammer bank more difficult and expensive to manufacture and to remove for servicing or replacement of the hammer bank in the field. Additionally, conventional hammer banks typically incorporate relatively complex, dual-pole-piece magnetics for the control of each hammer, which adds to their complexity and cost of manufacture.
Accordingly, there is a long felt but as yet unsatisfied need in the relevant industry for hammer bank designs that are both efficient and reliable, yet which are easier and lower in cost to manufacture and service.